Method of drawing sheet stock



Sept. 1, 1964 A. GLASSER 3,146,880

METHOD OF DRAWING SHEET s'rocx Filed March a, 1962 2 Sheets-Sheet 1 FIGI INVEN TOR.

ATTORNEYS Sept. 1, 1964 A. GLASSER 3,146,880

METHOD OF DRAWING SHEET s'rocx 2 Sheets-Sheet 2 Filed March 6, 1962 1 I I I I u I a I l I I l I 1 I I I I I 0 w gi -g g g INVENTOR.

ATTORNEYS United States Patent 3,146,880 METHOD OF DRAWING SHEET STOCK Alan Glasser, South Acton, Mass., assignor to Creative Consultants Corp., West Acton, Mass, a corporation of Massachusetts Filed Mar. 6, 1962, Ser. No. 177,830 7 Claims. (Cl. 2051) This invention relates to the cold drawing of sheet stock and more particularly comprises a new and improved method and apparatus for hydraulically applying forces to sheet stock to reduce its gage and increase its strength.

In cold drawing processes commonly used today, the gage of the sheet stock is reduced by applying compressive forces to each side of the sheet through one or a stack of rolls while simultaneously subjecting the sheet to tensioning forces in the plane of the sheet. The cold rolling process has certain inherent limitations. For example, with large rollers the power required to exert yielding pressures to the stock is extremely large. In addition, the rollers must necessarily be relatively large to possess the stiffness required to assure that the rolled stock has uniform thickness. While power requirements may be reduced by reducing roller size, this is only done with a corresponding sacrifice in roller stiflfness. Another inherent disadvantage of cold rolling metal is that the surface finish of the rolled sheet is dependent upon the finish of the rollers, and any imperfection in the surface of a roller is transferred to the stock.

An important object of this invention is to provide a cold drawing process for metals which does not have the disadvantages inherent in the cold rolling process.

To accomplish this and other objects, the method of this invention includes among its features the concept of applying compressive forces to the stock through the medium in which the stock passes, while simultaneously applying tensioning forces to it. This method is embodied in apparatus which includes a pair of spaced dies defining between them a passage through which the sheet to be drawn is directed. Feeding means are provided to direct the sheet through the passage, and a source of pressurized fluid is directed by flow lines against the sheet normal to its surfaces and transverse to the direction in which the sheet is fed. The cross-sectional area impinged by the pressurized fluid has as one dimension the sheet width and is in the order of a few thousandths of an inch in length, i.e., measured in the direction of sheet feed.

These and other objects and features of this invention, along with its incident advantages, will be better understood and appreciated from the following detailed description of one embodiment thereof, selected for purposes of illustration and shown in the accompanying drawing, in which:

FIG. 1 is a diagrammatic view of a system for cold drawing sheet metal in accordance with this invention;

FIG. 2 is an enlarged cross-sectional view of a portion of the system shown in FIG. 1; and

FIG. 3 is a cross-sectional view taken along the section line 3-3 of FIG. 2.

The system shown in FIG. 1 includes a pair of dies and 12 between which the sheet stock 14 is directed, and an hydraulic system 16 including a reservoir 18 for directing the fluid to the dies and return the fluid after it has impinged upon the sheet stock.

The sheet stock 10 is directed from roll 20 in the direction of arrow A through the passage 22 between the dies 10 and 12 to the take up roll 24. Each of the dies is provided with a pair of angularly disposed lower surfaces 27 and 28 with the surfaces 27 converging towards one another in the direction of the indicated movement of the sheet stock 14 and the surfaces 28 diverging from one 3,146,880 Patented Sept. 1, 1964 ice another in the same direction. Thus, the surfaces 27 and 28 define a gap or narrow throat 31 in the passage 22 which just slightly exceeds the thickness of the sheet stock 14 before it is drawn by the system.

In FIG. 2 the dies 10 and 12 are each shown to be provided with a very narrow gap 26 which define nozzles for directing fluid from the hydraulic system 16 to the sheet stock 14 at the narrow throat 31 of the passage 22. The gaps 26 in each of the dies are disposed normal to the plane of the stock 14 and as shown in FIG. 3 have a width w which just exceeds the width of the sheet stock 14. The length l of the gaps 26 is extremely small, that is, in the order of a few thousandths of an inch.

The nozzles 26 are connected to ducts 29 which are joined to a pressure equalizer 30 forming part of the hydraulic subsystem 16. The pressure equalizer 30 is supplied with fluid from an accumulator 32 connected to the outlet of pump 34 which supplies the fluid to the accumulator under extremely high pressures. The pump 34 in turn is connected to the reservoir 18.

The passage 22 between the dies 10 and 12 is closed at its ends by flexible wipers 36 which act as blades to retain the liquid in the gap 22. The sides of the passage may be closed by plates 37. The liquid is permitted to drain from the passage 22 into trough 38 which is connected to a return line 40 for directing the liquid collected by the trough back to the reservoir 18.

The system diagrammatically illustrated in FIG. 1 is capable of reducing the gage of the sheet stock to any desired value and is limited only by the pressure obtainable in the system. The system is not in any way encumbered by the inherent limitations of the cold rolling process alluded to above.

In operation, as the sheet stock is transferred from roll 20 to roll 24 through the throat or narrowest point 31 of the passage 22 defined by the opposed dies, and as the sheet is tensioned in the plane of the sheet by the tensioning mechanism represented diagrammatically at 42, the pump directs the liquid through the accumulator and pressure equalizer to the gaps 26 where they in turn direct the fluid against the opposite faces of the sheet in the throat 31. As the length l of the gaps 26 is extremely small, i.e. in the order of a few thousandths of an inch, as the fluid strikes the metal it is capable of exerting the extremely high pressures which are required to produce yielding of the material. This pressure applied over an extremely small area due to the minute length dimension must be adjusted so as to achieve yielding of the material without cutting through the stock. This pressure causes the sheet stock to yield and reduce in thickness or gage an amount determined by the fluid pressure. The gage of the drawn sheet may readily be regulated by varying the output pressure at the pump 34.

The following example of a typical application will suggest the order of magnitude of pressures that may be required in the practice of this invention. Assume that the gage of a thirty inch A.M. 355 stainless steel sheet is to be reduced from .015" to .012 and its tensile strength increased from 325,000 p.s.i. to 400,000 p.s.i. An hydraulic pressure of approximately 400,000 p.s.i. would be required and the passages 26 in the dies would have a dimension 1 of approximately .002" or .003". In this example, the throat 31 should exceed the original sheet gage by approximately .002"; that is, the throat should be approximately .017 in height.

From the foregoing it will be appreciated that the liquid medium through which the stock passes applies the pressure to achieve yielding and will not mar the surface of the stock. The amount of gage reduction is limited only by the pressure obtainable in the system and not by the diameter of rollers, as is the case in the cold rolling process. The amount of gage reduction may be varied readily merely by changing the output pressure of the pump and no delicate adjustment of roller pressure is required. No problems of mechanical alignment are encountered in this hydraulic cold drawing system as the liquid itself will serve to equalize the pressure appliedto the sheet across its Width as it passes through the throat 31 of the passage 22.

In the foregoing description one embodiment of this invention has been described in detail. Those skilledin the art will appreciate upon reading the foregoing that modifications may be made both of the process and apparatus without departing'from the spirit of this invention. Therefore, it is not intended that the breadth of this invention be determined by the single embodiment illustrated and described. Rather, it is intended that the breadth'of this invention be determined by the appended claims and their equivalents.

What is claimed is:

1. A method of drawing sheet stock comprising the steps of applying tensioning forces to the sheet in the plane of the sheet and directing a high pressure and high velocity stream of fluid to the upper and lower surfaces of the sheet from nozzles disposed a few thousandths of an inch from the surfaces and directed in a direction transverse of the tensioning forces sufficient to deform the sheet.

2. A method of drawing sheet stock comprising the steps of applying a high velocity, high pressure narrow stream of fluid across the entire width of the sheet at an angle to the plane of the sheet and at a pressure sufficient to deform the sheet,

and simultaneously applying tension to the sheet in the plane of and lengthwise of the sheet.

3. A method of drawing sheet stock comprising'the steps of directing the sheet through a pair of spaced dies separated by a distance just exceeding the thickness of the undrawn sheet,

applying tensioning forces to the sheet lengthwise of the sheet, and

simultaneously directing a narrow stream of fluid through the dies under pressure to the two sides of the sheet across the full width of the sheet at a pressure suflicient to deform the sheet.

4. A method of drawing sheet stock comprising the steps of directing the sheet through a pair of spaced dies separated by a distance just exceeding the thickness of the undrawn sheet,

applying tensioning forces to the sheet lengthwise of the sheet, and

simultaneously directing directly opposed narrow streams of fluid under presure through the dies to the two sides of the sheet across the full width of the sheet at a pressure sufficient-to deform the sheet.

5. A method as defined in claim 4 further characterized by the narrow streams of fluid being maintained in the order of a few thousandths of an inch in Width.

6. A method of drawing sheet stock comprising the steps of applying tensioning forces to the sheet in the plane of the sheet, and

directing streams of liquid in the orderof a few thousandths of an inch in thickness and at a pressure in the order of 400,000 p.s.i. simultaneously and in directions directly opposing one another to the upper and lower surfaces of the sheet transversely to the tensioning forces in order to deform the sheet.

7. A method as defined in claim 6 further characterized by the step of moving the sheet in a direction parallel to the tensioning forces while the streams of liquid are directed against the sheet.

References Cited in the file of this patent UNITED STATES PATENTS 293,011 Hall et a1 Feb. 5, 1884 345,816 Tilghman July 20, 1886 1,779,478 Leech Oct. 28, 1930 2,226,500 Matthews Dec. 24, 1940 2,271,773 McIlvried Feb. 3, 1942 2,332,069 Gettig Oct. 19, 1943 2,785,924 Kane Mar. 19, 1957 3,054,162 Amtmann Sept. 18, 1962 

1. A METHOD OF DRAWING SHEET STOCK COMPRISING THE STEPS OF APPLYING TENSIONING FORCES TO THE SHEET IN THE PLANE OF THE SHEET AND DIRECTING A HIGH PRESSURE AND HIGH VELOCITY STREAM OF FLUID TO THE UPPER AND LOWER SURFACES OF THE SHEET FROM NOZZLES DISPOSED A FEW THOUSANDTHS OF AN INCH FROM THE SURFACES AND DIRECTED IN A DIRECTION TRANSVERSE OF THE TENSIONING FORCES SUFFICIENT TO DEFORM THE SHEET. 